This invention relates to an optical fiber cable connecting device and, more particularly, to an optical fiber cable connecting device that enables an optical fiber cable to be connected to an ordinary connector in a simple manner.
It is sometimes desired to measure optical fiber characteristics such as fiber loss using an optical power meter. In such case a connecting device is employed to connect the optical fiber to a sensor which forms part of the optical power meter. An example of a conventional connecting device is illustrated in FIGS. 1A, 1B and 1C. Attached to the sensor, denoted at numeral 10, is a connector 14 which permits the connection of a fiber cable plug 12. Such is the arrangement for ordinary use. To connect an optical fiber cable 16 directly to the sensor 10, however, the connector 14 is detached and replaced by a special connector 18 that enables the connection of a connecting device 20. The latter is so constructed as to grasp the optical fiber cable 16 between fixing portions 22 and 24. Specifically, the fixing portion 22 has a V-shaped channel 26 for receiving the optical fiber cable 16, a retaining member 28 consisting of a spring for retaining the optical fiber cable 16 in the V-shaped channel 26, and a V-shaped channel 30 which is a continuation of the V-shaped channel 26 for receiving solely the bare fiber 16a of the optical fiber cable 16. The fixing portion 22 further includes a fitting portion 32 constituting a unitary body with the extremity 22a of the fixing portion 22 in order to permit the latter to be plugged into the receptacle 18a of the special connector 18, and a magnet 34b which, when the optical fiber cable 16 has been inserted between the fixing portions 22 and 24, is attracted to a magnet 34a provided on the fixing portion 24 in order to hold the fiber cable firmly in place.
The connecting device having the foregoing construction requires the provision of the special connector for the connection to the sensor. This means that a worker must go to the trouble of attaching and detaching the connector as the case requires. Another problem which is encountered relates to the V-shaped channels that receive the optical fiber cable and bare fiber when the latter are clamped within the connecting device. Specifically, and particularly with regard to the V-shaped channel that receives the bare fiber, it is extremely difficult to retain the bare fiber firmly within the V-shaped channel without any displacement in its optical axis because the bare fiber is available in two diameters of 125 and 150 microns. Any displacement in the optical axis will cause an increase in the spot size projected on the surface of the sensor as well as an increase in the error of low-input level measurements. Still another disadvantage of the conventional connecting device is its large size which is necessitated by the fact that the optical fiber cable is held in place by the clamping-type arrangement.